Phase change material incorporated paper pulp sludge/gypsum composite reinforced by slag and fly ash for energy efficient buildings: Solar thermal regulation, embody energy, sustainability index and cost analysis

This study focuses on the reuse of some industrial wastes in the development of innovative building materials and the thermal performance, environmental impacts and cost estimates of the gypsum composite material developed in the case of a phase change material impregnation. Lauryl alcohol (LA) was impregnated into paper pulp sludge (PPS) up to 45 % by weight without leakage to obtain shape-stable composites. The LA impregnated PPS (PPS/LA) was replaced with PPS at 50 % and 100 % by weight in gypsum composite. Characteristics of shape-stable composites were studied. Also, the physical, mechanical, thermal properties and solar thermoregulation tests of the produced gypsum composites were examined in addition to the embodied energy, CO₂ emissions and cost analysis. The melting and solidification enthalpies of PPS/LA were found to be 100.4–100.1 J/g, with only a 0.5 % reduction in latent heat storage capacity after 500 cycles, and approximately 3 % after 1500 cycles. Although the presence of PPS/LA in the gypsum composite caused a slight decrease in compressive strength, it significantly improved solar thermoregulation performance, maintaining ambient temperatures 2.55 °C to 5 °C warmer at night and 5.3 °C to 13.8 °C cooler during the day. Gypsum composites containing the PPS/LA offer a suitable alternative for energy-efficient sustainable building application by reusing around 57 % of three different industrial wastes providing a waste-reducing environmental approach and a high level of indoor thermal comfort.